Develop Reference

How to validate decimal input not allowing alone "." and empty field?

I'm writing a calculator on Android Studio, in Java, and the app crashes if the user call the result with a dot "." alone or let the EditText field in blank.
I'm looking for a solution for not allowing these two conditions happening, together or individualy, in each of the three fields.
I've already tried TextWatcher and if/else but without success.
The .xml file where the editText field are designed is already set for decimalNumber.
I've already tried this:
if(myfieldhere.getText().toString().equals(".")){myfieldhere.setText("0");}
For each "valor line" and else for the "finalresult" line if everything is fine. Both inside the setOnClickListener block. This is my code:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.peso_layout);
result = findViewById(R.id.layresult);
conc = findViewById(R.id.layconc);
dose = findViewById(R.id.laydose);
peso = findViewById(R.id.laypeso);
calc = findViewById(R.id.laycalcpeso);
calc.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
float valor1 = Float.parseFloat(peso.getText().toString());
float valor2 = Float.parseFloat(conc.getText().toString());
float valor3 = Float.parseFloat(dose.getText().toString());
float finalresult = valor1 * valor2 * valor3;
result.setText("The result is: " + finalresult);
}
});
}
The ideal output should be the app not crashing if these two conditions happen and sending an error message to the user that input is invalid.
What i'm receiving is the app crashing.
Thank you very much. I'm very beginner in Java and I'm few days struggling with this.

Dear Friend, Your directly trying to convert string input into float and then after your check value but do your code like Below.
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
EditText edt1,edt2;
TextView txtans;
Button btnsum;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
edt1=findViewById(R.id.edt1);
edt2=findViewById(R.id.edt2);
txtans=findViewById(R.id.txtans);
btnsum=findViewById(R.id.btnsum);
btnsum.setOnClickListener(this);
}
#Override
public void onClick(View v) {
if(v.getId()==R.id.btnsum){
float n1,n2;
String value1=edt1.getText().toString();
String value2=edt2.getText().toString();
if(value1.equals("") || value1.equals(".")){
n1=0;
}else {
n1= Float.parseFloat(value1);
}
if(value2.equals("")|| value2.equals(".")){
n2=0;
}else{
n2= Float.parseFloat(value2);
}
float ans=n1+n2;
txtans.setText(ans+"");
}
}
}
See In above code, First get value from edittext and then check wheather it contain null or "." inside it. if it contains then store 0.0 value in some variable. then after make sum and display in textbox.

calc.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View view) {
String myvalor = myfieldhere.getText().toString();
if(myvalor.equals(".") || myvalor.isEmpty())
{
// toast error : incorrect value
return;
}
try
{
float valor1 = Float.parseFloat(peso.getText().toString());
float valor2 = Float.parseFloat(conc.getText().toString());
float valor3 = Float.parseFloat(dose.getText().toString());
float finalresult = valor1 * valor2 * valor3;
result.setText("The result is: " + finalresult);
}
catch(Exception exp){// toast with exp.toString() as message}
}
});

use TextUtils for check empty String its better
if(TextUtils.isEmpty(peso.getText().toString())||
TextUtils.isEmpty(conc.getText().toString())||
TextUtils.isEmpty(dose.getText().toString())){
return;
}

Class variable random number... always the same? Android.

I am working through a Udemy course and we're building a basic "Higher or Lower" app. My app essentially works, however the random number it chooses for us to guess is always the same no matter how many times I destroy and relaunch the activity.
My MainActivity.java:
//mad import statements here
public class MainActivity extends AppCompatActivity {
int correctNumber;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
int correctNumber = generateNum();
}
protected int generateNum(){
Random rand = new Random();
int randNum = rand.nextInt(100);
return randNum;
}
protected void numberEval(View view) {
EditText enteredNumber = (EditText) findViewById(R.id.numberEntry);
String numberString = enteredNumber.getText().toString();
Button pressMe = (Button) findViewById(R.id.button);
int numToEval = Integer.parseInt(numberString);
String result;
TextView showWinLose = (TextView) findViewById(R.id.winLoseText);
if (numToEval > correctNumber) {
result = "Too high!";
} else if (numToEval < correctNumber) {
result = "Too Low!";
}else {
result = "You guessed it!";
}
showWinLose.setText(result);
}
}
Super super basic, yes? Originally, my numberEval() method called generateNum(), but then I realized it was generating a new number to guess every time I pressed the button. So I set it the way it was here, where onCreate() generates correctNumber only once and correctNumber is now a class variable. Now it doesn't generate a new number every button click, but it won't seem to generate a new number at all. It's stuck at 0 no matter how any times I launch, close, relaunch, etc. the app.
How can I fix this? Thanks in advance.

public class MainActivity extends AppCompatActivity {
int correctNumber;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
int correctNumber = generateNum();
}
// ...
}
The last line in onCreate() declares a local variable named correctNumber. This hides the class field with the same name and is only available inside onCreate(). To fix the problem, remove int from this line so that you use the class field instead.

Compare the result of two TextViews Java/Android

I'm making a simple very simple android math game. But I cant manage to compare two TextViews to let the user know if they calculated correct or not???
Im not comparing them correctly as my if/else statement is only giving me the else output??
public class PlayActivity extends AppCompatActivity {
EditText number1;
EditText number2;
TextView result;
Button addNumbers;
TextView equalW;
TextView equalL;
TextView generate;
double num1,num2,sum;
Random r = new Random();
public View.OnClickListener listener = new View.OnClickListener() {
#Override
public void onClick(View v) {
generate = (TextView)findViewById(R.id.textViewGenerate);
int generated = r.nextInt(101);
generate.setText(Integer.toString(generated));
}
};
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_play);
number1 = (EditText)findViewById(R.id.editTextNumber1);
number2 = (EditText)findViewById(R.id.editTextNumber2);
result = (TextView)findViewById(R.id.textViewSum);
addNumbers = (Button)findViewById(R.id.buttonAdd);
equalL = (TextView)findViewById(R.id.textViewLose);
equalW = (TextView)findViewById(R.id.textViewWin);
Button buttonGenerate = (Button)findViewById(R.id.buttonGenerate);
buttonGenerate.setOnClickListener(listener);
addNumbers.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
num1 = Double.parseDouble(number1.getText().toString());
num2 = Double.parseDouble(number2.getText().toString());
sum = num1 + num2;
result.setText(Double.toString(sum));
if (generate.getText().toString().equals(result))
{
equalW.setText("Answer is correct");
}
else {
equalL.setText("lose");
}
}
});
}

You have one obvious problem and another lurking problem.
The obvious one: You have to compare a String with a String and not with a TextView. Hence replace if (generate.getText().toString().equals(result)) with if (generate.getText().toString().equals(result.getText().toString())).
The lurking one: If you see closely, sum is set as String in result and generated is set as String in generate. sum is of data type double and generate is of data type int. Comparing both will cause problem. This is like comparing "10".equals("10.0"). This is error prone. You need to set both these fields to a common data type.

Change if condition as:
if (generate.getText().toString().equals(result.getText().toString()))
{
}
Because result is view so call getText method for comparing String values.

result is textview so you have to write
if (generate.getText().toString().equals(result.getText().toString))

2D array in android without specify dimention length

public class MainActivity extends ActionBarActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
final String[][] Array2D = new String[2][10];
Button enter =(Button)findViewById(R.id.Button1);
final EditText valueEditText=(Button)findViewById(R.id.EditText1);
final EditText xEditText=(Button)findViewById(R.id.EditText1);
final EditText yEditText=(Button)findViewById(R.id.EditText1);
enter.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String value =valueEditText.getText().toString();
int x=Integer.valueOf(xEditText.getText().toString());
int y=Integer.valueOf(yEditText.getText().toString());
Array2D[x][y]=value;
}
});
}
}
I am working on a project with 2D String array. At every click, I enter new addresses and values to be entered in that address.
The problem is: I want to do that with dynamic array (without defining specific dimensions for long and width)
Could any one can help me please ???

The length of an array is fixed.
You should use a List<List<String>> instead.

Solution to equation won't display? (no errors being reported on my end)

So I managed to take 4 different activities involving 4 variables and wrote them in this kind of format:
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_step1);
Button c = (Button) this.findViewById(R.id.continue1);
final EditText input = (EditText) findViewById(R.id.enterscore);
input.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
String score1 = input.getText().toString();
Double.parseDouble(score1);
{ Intent myintent = (new Intent(step1.this,step2.class));
myintent.putExtra("SCORE1",score1);
startActivity(myintent);
}
On my final activity the one that's suppose to display the solution I have coded the following:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_answer);
}
public void solutionf(View v) {
Bundle extras = getIntent().getExtras();
if(extras!=null){
double score1 = extras.getDouble("SCORE1");
double score2 = extras.getDouble("SCOREF");
double l2 = extras.getDouble("L2");
double l3= extras.getDouble("L3");
double solution= (((score2-score1)/l2)*l3);
String resultString = "Result:" +solution;
TextView resultText= (TextView) findViewById(R.id.solution);
resultText.setText(resultstring);
}
}
}
Why won't the final solution display? I've checked over to make sure everything matches up in terms of the doubles that are set in the activities. Could it be I didn't properly bring the variables over from the previous activities through error on my code?
Any help to getting the solution to show would be appreciated!

Unless a part of your code is missing, solution() is never called.
Add a call to this function in onCreate of your second activity, it should help.